The present invention relates generally to plastic containers and closures therefore; specifically to a plastic paint container and a closure therefore.
With the increased efficiency of molding techniques for various types of polymeric materials, the container industry, among others, is experiencing a conversion to polymeric materials to take advantage of the many beneficial characteristics of the various polymers which the packaging industry has come to employ. Unlike many other sectors of the packaging industry, the paint container industry has not achieved a successful conversion from the standard steel paint can that has been in existence for many years. While these steel cans provide high structural integrity and good sealing, they are also susceptible to denting and rusting.
Filling and sealing of paint containers is typically performed by automated equipment. This usually includes filling a container with a white base paint and then capping the container with a plug (commonly referred to as a lid). Between the filling operation and the capping operation, the plug is placed on the filled container by a lid dropper/placer. At the lid dropper/placer the plugs are manually loaded into a trough and indexed down onto the containers. Accordingly, the profile of the plug must consider its movement through the indexing trough of this industry standard equipment, so that the plugs do not jam, as well as the requirements of sealing the container.
As the plug is transferred to the container, it must xe2x80x9cfind it""s centerxe2x80x9d and the ring (the portion of the container designed to accept the plug) and plug should be profiled to facilitate this. The plug and corresponding ring must allow for insertion of the plug by automated equipment as well as re-sealing by the consumer. However, the plug and ring must also provide security against unwanted release of the plug from the ring while allowing the consumer to remove the plug without undue force.
Typically, after paint containers are filled with the white base paint and then capped, a label and then a bail (i.e. handle) are applied, and container is then packed in a carton. Alternatively, some manufacturers may label, bail and then fill. Cartons of full containers are shipped and stacked vertically in warehouses on pallets and then re-shipped to retailers for sale. The retailer removes the plug, ads tint color and re-closes the plug. Alternatively, some retailers punch a hole in the plug, add tint color through the hole and install a plastic stopper in the hole.
When paint containers are filled and capped, air is typically trapped in the headspace between the liquid level and the plug. When the plug compresses the air, the internal pressure of the container is increased and acts in conjunction with the weight of the liquid product forcing the bottom profile of the container to distend. Extensive distention may interfere with the proper operation of some capping, bailing or packaging equipment and may render the containers unstable in stacking.
Paint containers are generally stored in warehouses in vertical stacks up to, or exceeding, 12 containers high. A container""s ability to sustain an axial load is therefore important to prevent buckling of the container under the weight of those containers above it. Prior to this invention, it was thought that the axial load resistance of a plastic container would be directly proportional to the plastic material and sidewall thickness of the container. However, because injection molding the body of a plastic container requires that the sidewall be at some minimal angle to its central axis to allow release of the sidewall from the mold, prior plastic containers gradually thinned the sidewall thickness from bottom to top in order to provide the necessary release angel. The thickness at the base of such sidewalls consumed high amounts of resin.
Accordingly, there is a need for a plastic container adapted to contain standard volumes of paint and which will allow for relatively easy opening and sealing of the plug without being susceptible to accidental opening and which container will have dimensions necessary to be compatible with standard filling, capping, labeling and bailing equipment in the industry while being capable of sustaining the axial loading and other rigors to which paint cans are typically subjected.
It is a primary objective of the present invention to provide a paint can that is resistant to denting and rusting.
It is an object of the invention to provide a container having a plug closure capable of sealing the inside of the container from unwanted exposure to the atmosphere while minimizing insertion force of the plug.
It is another object of the invention to provide a container having a plug closure capable of sealing the inside of the container from unwanted exposure to the atmosphere while minimizing removal force of the plug without undue exposure to accidental release of the plug from the container.
It is a further object of the invention to provide a container having a body capable of sustaining axial loading while minimizing material necessary to construct the body.
It is yet another object of the invention to provide a container having high hoop strength resistant to ovalizing.
It is another object of the present invention to provide a container having a bottom panel capable of preventing substantial distention while minimizing material necessary to construct the body.
It is an additional object of the present invention to provide a polymeric container having a plug closure capable of sealing the inside of the container from unwanted exposure to the atmosphere while minimizing insertion force of the plug.
It is another object of the invention to provide a polymeric container having a plug closure capable of sealing the inside of the container from the unwanted exposure to atmosphere while minimizing removal force of the plug.
It is a further object of the invention to provide a polymeric container having a body capable of sustaining axial loading while minimizing material necessary to construct the body.
It is yet another object of the invention to provide a polymeric container having high hoop strength resistant to ovalizing.
It is another object of the present invention to provide a polymeric container having a bottom panel capable of preventing substantial distention while minimizing material necessary to construct the body.
It is an additional object of the invention to provide a polymeric paint container.
It is still another object of the invention to provide a container constructed a polymeric resin to approximate the dimensions of a steel paint can necessary to allow manipulation of the container by standard filling and handling equipment employed for the steel paint can.